In a photolithography process for manufacturing a semiconductor device, photoresist is coated on a surface of a semiconductor substrate (hereinafter, simply referred to as a “substrate” or a “wafer”), and a mask pattern is exposed on the photoresist and then is developed, so that a resist pattern is formed on the surface of the wafer.
In such a photolithography process, a developing process may be performed by, e.g., a puddle method or a dipping method. By way of example, in the puddle method, the developing process is performed by supplying a developing solution to the wafer, whereas in the dipping method, the developing process is performed by submerging the wafer in the developing solution. Then, in both methods, a rinse solution such as pure water which is used as a cleaning solution is supplied to the wafer to wash away the developing solution. Thereafter, to remove the rinse solution from the wafer, a drying process is performed by blowing air to the wafer or by rotating the wafer.
Meanwhile, along with the recent trend for higher degree of miniaturization of semiconductor devices, resist patterns are getting finer and becoming to have a higher aspect ratio. Since such resist patterns are microscopic and have a high aspect ratio, when the rinse solution is removed from between the patterns during the drying process, an attraction force may be generated between the patterns due to a surface tension of the rinse solution, thereby resulting in a so-called “pattern collapse”. In order to prevent the pattern collapse, there has been proposed a developing method for supplying, onto a substrate, an organic solvent having a smaller surface tension than that of the rinse solution before the drying process is performed.
By way of example, in order to prevent pattern collapse in the process of removing a rinse solution, there has been proposed a developing method for supplying a rinse solution to a substrate having a developed resist pattern and supplying a fluorine-containing organic solvent to the substrate onto which the rinse solution has been supplied (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent Laid-open Publication No. 2003-178943
However, when a processing solution containing the organic solvent is supplied to the substrate onto which the rinse solution has been supplied, the following problems may be caused.
As a next-generation exposure technology, EUV (Extreme Ultra-Violet) exposure is under development, and further miniaturization of a resist pattern is progressing. Besides, when an etching is performed using the miniaturized resist pattern as a mask to transfer the resist pattern onto an etching target film under the resist pattern, there may be a case in which a height of a resist pattern is increased depending on etching conditions. If the height of the resist pattern increases, an aspect ratio with respect to a width of the resist pattern may also be increased. Such an increase of the aspect ratio of the resist pattern may cause pattern collapse depending on a relationship between a surface tension of pure water and a contact angle of the pure water with respect to the resist pattern, when the water is removed from the resist pattern during the drying process after the developing process and the rinse process.
It has been attempted to prevent pattern collapse by hydrophobicizing a surface of a resist pattern through the use of a hydrophobicizing agent instead of the processing solution including the fluorine-containing organic solvent. Since, however, the hydrophobicizing solution is a high-price liquid chemical, cost for processing the substrate may be increased.
Furthermore, the pattern collapse may occur not only in the developing process but also in various subsequence substrate processes performed after the resist pattern is developed. For example, the pattern collapse may occur in a cleaning process for cleaning the substrate on which the resist pattern is formed.